Effect of adaptive beamforming and noise reduction algorithms on speech intelligibility and noise tolerance in bimodal cochlear implant users.

OBJECTIVE: To evaluate the effect of a directional microphone (beamformer) and continuous noise reduction algorithms (CNRs) in bimodally aided cochlear implant (CI) users and to find the optimum hearing aid (HA) and CI settings of the beamformer and CNRs. METHODS: Speech reception threshold (SRT) and acceptable noise level (ANL) were assessed in twelve adult CI users for unilateral CI, unilateral HA and bimodal listening. To assess the effect of the UltraZoom beamformer and the ClearVoice™ and NoiseBlock CNRs on SRT and ANL, speech was presented from the front in multi-source speech-shaped noise. RESULTS: With unilateral CI, application of UltraZoom resulted in a significant improvement of the median SRT and ANL by 3.8 and 4.3 dB, respectively. For bimodal listening with UltraZoom, a significant improvement of 3.5 dB in median SRT was found. There was no significant effect of using the CNRs on speech intelligibility in noise or noise tolerance in either listening condition. CONCLUSION: UltraZoom should be applied on the CI to improve speech intelligibility in face to face conversations with multi-source background noise. However, due to the heterogeneous data, no recommendations for the settings of UltraZoom on the HA or of ClearVoice/NoiseBlock on either device can be given. TRIAL REGISTRATION: German Clinical Trials Register identifier: DRKS00010807.

Benefit of directional microphones for unilateral, bilateral and bimodal cochlear implant users.

OBJECTIVE: To compare the standard T-Mic setting to UltraZoom and StereoZoom in 10 unilateral cochlear implant (CI) users, 10 bimodal device users and 10 bilateral CI users as well as a normal hearing (NH) reference group (n = 10). METHOD: Speech reception thresholds were measured using the Oldenburg sentence test in noise. Speech was presented from the front at 0°, noise was presented from five loudspeakers spaced at ±60°, ±120°, 180° (setup A) or from four loudspeakers in the front hemisphere at ±30°, ±60° and one at 180° (setup B). RESULTS: There was a significant advantage for UltraZoom and StereoZoom for all groups in both setups. The largest advantage was for StereoZoom in the bilateral group (setup A, 5.2 dB, P < 0.001 and B, 3.4 dB, P < 0.001) There was a significant advantage for StereoZoom over UltraZoom in the bimodal group (setup A, P < 0.01 and B, P < 0.05) and in the bilateral group (P < 0.01, setup B only). The bilateral group performed as well as the normally hearing group in both setups and the bimodal group performed as well in setup A. There was a significant benefit of 1.8 dB for ClearVoice over UltraZoom alone for the unilateral group. CONCLUSIONS: UltraZoom and StereoZoom provided a clinically and statistically significant benefit over the T-Mic condition. The largest gain was shown for StereoZoom in the bimodal and bilateral groups. The use of StereoZoom enabled the bilateral group to perform as well as the normally hearing group in both the challenging speaker setups. However, real life environments might provide an even greater challenge than the conditions tested here.

Impact of Microphone Configuration on Speech Perception of Cochlear Implant Users in Traffic Noise.

OBJECTIVE: The aim of this study was to investigate the impact of microphone configuration and noise reduction algorithm on speech perception of cochlear implant (CI) users in a moving noise setup. METHOD: Eleven CI users provided with Advanced Bionics implant systems participated in this study. All tests were conducted with three different microphone settings: (a) omnidirectional behind the ear (BTE), (b) inside the pinna (ITP), and (c) adaptive directional microphone (adaptive beamformer, ABF). Speech reception thresholds (SRTs) were measured using the Oldenburg sentence test in a moving noise source condition. Furthermore, the effect of a noise reduction algorithm on speech perception was measured in a condition with an additional static noise source. RESULTS: The ABF setting significantly improved SRT by 5.7 dB compared with the BTE microphone, and by 4.7 dB compared with the ITP microphone in the moving noise condition. In the presence of an additional static noise source, there was a significant improvement in SRT of 0.9 dB with the use of NR in addition to ABF. CONCLUSION: Adaptive beamforming can significantly improve speech perception in moving noise. Depending on the noise condition, the combination of ABF with NR can provide additional benefit.

Multicentre Evaluation of the Naída CI Q70 Sound Processor: Feedback from Cochlear Implant Users and Professionals.

The aim of this survey was to gather data from both implant recipients and professionals on the ease of use of the Naída CI Q70 (Naída CI) sound processor from Advanced Bionics and on the usefulness of the new functions and features available. A secondary objective was to investigate fitting practices with the new processor. A comprehensive user satisfaction survey was conducted in a total of 186 subjects from 24 centres. In parallel, 23 professional questionnaires were collected from 11 centres. Overall, there was high satisfaction with the Naída CI processor from adults, children, experienced and new CI users as well as from professionals. The Naída CI processor was shown as being easy to use by all ages of recipients and by professionals. The majority of experienced CI users rated the Naída CI processor as being similar or better than their previous processor in all areas surveyed. The Naída CI was recommended by the professionals for fitting in all populations. Features like UltraZoom, ZoomControl and DuoPhone would not be fitted to very young children in contrast to adults. Positive ratings were obtained for ease of use, comfort and usefulness of the new functions and features of the Naída CI sound processor. Seventy-seven percent of the experienced CI users rated the new processor as being better than their previous sound processor from a general point of view. The survey also showed that fitting practices were influenced by the age of the user.

Assessment of 'Fitting to Outcomes Expert' FOX™ with new cochlear implant users in a multi-centre study.

OBJECTIVE: To compare the fitting time requirements and the efficiency in achieving improvements in speech perception during the first 6 months after initial stimulation of computer-assisted fitting with the Fitting to Outcome eXpert' (FOX) and a standard clinical fitting procedure. METHOD: Twenty-seven post-lingually deafened adults, newly implanted recipients of the Advanced Bionics HiRes 90K™ cochlear implant from Germany, the UK, and France took part in a controlled, randomized, clinical study. Speech perception was measured for all participants and fitting times were compared across groups programmed using FOX and conventional programming methods. RESULTS: The fitting time for FOX was significantly reduced at 14 days (P < 0.001) but equivalent over the 6-month period. The groups were not well matched for duration of deafness; therefore, speech perception could not be compared across groups. DISCUSSION: Despite including more objective measures of performance than a standard fitting approach and the adjustment of a greater range of parameters during initial fitting, FOX did not add to the overall fitting time when compared to the conventional approach. FOX significantly reduced the fitting time in the first 2 weeks and by providing a standard fitting protocol, reduced variability across centres. CONCLUSIONS: FOX computer-assisted fitting can be successfully used at switch on, in different clinical environments, reducing fitting time in the first 2 weeks and is efficient at providing a usable program.

Evaluation of the 'Fitting to Outcomes eXpert' (FOX®) with established cochlear implant users.

OBJECTIVES: To evaluate the possible impact of 'Fitting to Outcomes eXpert (FOX(®))' on cochlear implant (CI) fitting in a clinic with extensive experience of fitting a range of CI systems, as a way to assess whether a software tool such as FOX is able to complement standard clinical procedures. METHODS: Ten adult post-lingually deafened and unilateral long-term users of the Advanced Bionics(TM) CI system (Clarion CII or HiRes 90K(TM)) underwent speech perception assessment with their current clinical program. One cycle 'iteration' of FOX optimization was performed and the program adjusted accordingly. After a month of using both clinical and FOX programs, a second iteration of FOX optimization was performed. Following this, the assessments were repeated without further acclimatization. RESULTS: FOX prescribed programming modifications in all subjects. Soundfield-aided thresholds were significantly lower for FOX than the clinical program. Group speech scores in noise were not significantly different between the two programs but three individual subjects had improved speech scores with the FOX MAP, two had worse speech scores, and five were the same. CONCLUSION: FOX provided a standardized approach to fitting based on outcome measures rather than comfort alone. The results indicated that for this group of well-fitted patients, FOX improved outcomes in some individuals. There were significant changes, both better and worse, in individual speech perception scores but median scores remained unchanged. Soundfield-aided thresholds were significantly improved for the FOX group.

Everyday listening questionnaire: correlation between subjective hearing and objective performance.

OBJECTIVES: Clinical experience has demonstrated that speech understanding by cochlear implant (CI) recipients has improved over recent years with the development of new technology. The Everyday Listening Questionnaire 2 (ELQ 2) was designed to collect information regarding the challenges faced by CI recipients in everyday listening. The aim of this study was to compare self-assessment of CI users using ELQ 2 with objective speech recognition measures and to compare results between users of older and newer coding strategies. METHODS: During their regular clinical review appointments a group of representative adult CI recipients implanted with the Advanced Bionics implant system were asked to complete the questionnaire. The first 100 patients who agreed to participate in this survey were recruited independent of processor generation and speech coding strategy. Correlations between subjectively scored hearing performance in everyday listening situations and objectively measured speech perception abilities were examined relative to the speech coding strategies used. RESULTS: When subjects were grouped by strategy there were significant differences between users of older 'standard' strategies and users of the newer, currently available strategies (HiRes and HiRes 120), especially in the categories of telephone use and music perception. Significant correlations were found between certain subjective ratings and the objective speech perception data in noise. CONCLUSIONS: There is a good correlation between subjective and objective data. Users of more recent speech coding strategies tend to have fewer problems in difficult hearing situations.

Performance of the Harmony™ behind-the-ear processor with the first generation of Advanced Bionics™ implant systems.

OBJECTIVES: When new cochlear implant (CI) sound processors are being introduced by the manufacturers, usually the newest generation implants benefit first from the new technology in order to release the full potential of the new hardware. Subsequently, for the Advanced Bionics system the Harmony behind-the-ear processor was only compatible to the newer generation implants, i.e. the CII and HiRes90K, at the time of market release. After further development of a new Digital Signal Processing code the Harmony could also support the first implant generation, the 'C1' (Clarion 1.0 and 1.2). This study reports on a field trial with a new sound processor designed to be used with older generation CIs from Advanced Bionics, focussing on ergonomic and performance benefits. METHODS: Speech perception tests (Freiburger monosyllables, HSM sentence tests) were performed at a baseline appointment with the subject's clinical processor, followed by the fitting of the Harmony. After a 1 month take-home period the tests were repeated with the Harmony. Additionally, subjective evaluation through questionnaires and a structured interview were administered after upgrading to the sound processor 'C1 Harmony'. Adult users of Advanced Bionics C1 series CIs (n = 29) participated in this study. RESULTS: The new processor provided superior performance in many, though not all, of the speech recognition measurements. Subjective reports indicated certain practical benefits from the new processor, particularly for previous users of body-worn processors. Overall, 80% of the subjects preferred the new processor. CONCLUSION: The positive outcomes from this trial have resulted in the decision to make the new C1 Harmony processor available to all existing users of the early C1 devices.

Results of a pilot study with a signal enhancement algorithm for HiRes 120 cochlear implant users.

OBJECTIVE: Cochlear implant users still experience severe limitations regarding sound quality, music appreciation, and speech perception in adverse listening situation. To improve hearing in noisy environments, the incorporation of signal enhancement algorithms was initiated. METHOD: The study group consisted of 13 postlingually deafened adults using HiRes 120. Participants were fitted with 2 versions of the noise reduction algorithm: a moderate and a strong setting. In an immediate session, the HSM sentence test in speech-shaped noise was administered using the clinical program as well as both noise reduction programs. Participants were asked to try all 3 programs in everyday listening situations at home and provide a rating of sound quality and speech perception via a questionnaire (Abbreviated Profile of Hearing Aid Benefit). RESULTS: During the fitting, no difficulties were encountered, and all participants accepted the noise reduction programs without any acclimatization. All participants achieved better results with both noise reduction programs in the HSM sentence test in noise compared with the clinical program. Group mean speech perception scores were highly significantly better for the ClearVoice settings compared with the clinical program score. The majority preferred one of the ClearVoice conditions, with 4 participants for the strong and 3 for the moderate setting. CONCLUSION: Our results demonstrate a real potential benefit for noise reduction algorithms in cochlear implant processors. Although algorithm parameters were not optimized individually, a significant improvement could still be achieved. Further investigation is required to develop fitting guidelines and achieve parameter optimization.

Cochlear implantation in unilateral deaf subjects associated with ipsilateral tinnitus.

OBJECTIVE: In subjects who are deaf and who also have tinnitus in the affected ear, tinnitus treatments based on acoustic input are impossible. On the other hand, tinnitus suppression using electric stimulation has been reported to be successful. Therefore, a study was initiated to investigate the potential of cochlear implantation (CI) in unilateral deaf subjects regarding tinnitus suppression, device acceptance, and restoration of spatial hearing. METHOD: Five subjects with severe to profound unilateral deafness having also ipsilateral tinnitus were enrolled. In monthly visits, the speech processor program was optimized, and the hearing performance as well as tinnitus were monitored. In addition, it was investigated whether the CI improves hearing in adverse listening situations when combined with the normal hearing side. RESULTS: In 3 participants, the tinnitus was significantly suppressed while wearing the device. In the other 2 participants, the tinnitus could be reduced in certain situations. Speech perception tests revealed a significant benefit with the CI in combination with the normal-hearing side for 3 participants. All participants accepted the device in a clinical setting; adaptation of the frequency allocation was not required. CONCLUSION: Improvements were found regarding the hearing and the tinnitus. Not all participants benefit from the CI to the same degree and in the same situations.The results indicate that cochlear implantation in subjects with unilateral severe to profound hearing loss and ipsilateral tinnitus may be beneficial on a case-to-case basis. Further work needs to be performed to define the appropriate indication criteria.

Investigation of pitch discrimination and the effect of learning for virtual channels realized by current steering.

CONCLUSION: As virtual channels could be perceived by the majority of implant users, they promise potential for advanced speech coding strategies, providing enhanced spectral resolution. An improvement in resolution was found from first stimulation up to 6 months afterwards. OBJECTIVE: Independent current sources allow distribution of the current between adjacent electrode contacts in a defined ratio, thus steering the current. The goal of our study was to investigate a) whether all users were able to distinguish between adjacent physical channels, b) how many users could perceive a distinct pitch as the current was steered between two adjacent contacts and c) whether a learning effect was observed. SUBJECTS AND METHODS: A pitch ranking measurement was performed during an acute test session for a group of 39 cochlear implant users. The results were analysed with respect to the implanted electrode system. The learning process during the first 6 months after implantation was investigated for a selected subgroup. RESULTS: About half of the study participants were able to perceive intermediate channels; 5% were able to discriminate more than eight intermediate channels, which correspond to half of the physical channels. A wide variation was found across the array.

Evaluation of the Harmony soundprocessor in combination with the speech coding strategy HiRes 120.

OBJECTIVE: The Advanced Bionics Harmony BTE processor was developed to support the new speech coding strategy HiRes 120 with a resolution of 120 channels based on "current steering." Compared with the previous Auria, the front end has been re-designed and power consumption reduced. STUDY DESIGN: HiRes 120 as well as the impact of the improved Harmony processing concerning a better speech understanding were evaluated. Subject's performance was evaluated using a test battery of the Hochmair-Schulz-Moser (HSM) sentence test and questionnaires regarding general sound quality, music perception, battery life time and processor handling. PATIENTS: In the first study group, 11 postlingually deafened adult subjects participated with a minimum of 9 months experience. The second study group consisted of 14 postlingually deafened adult subjects with a minimum of 2 years experience. INTERVENTIONS: Tested were the 2 speech coding strategies HiRes and HiRes 120 on the Harmony and the clinical system, respectively. MAIN OUTCOME MEASURES: Speech perception tests in quiet, in CCITT noise, as well as with a competing talker, questionnaires regarding sound quality and handling and perceptual channel tests. RESULTS: A total of 84% showed a clear preference for the Harmony processor compared with their previous processor with HiRes. The speech test results showed a 7.7% average increase in the HSM sentence test with 5 dB SNR competing talker. CONCLUSION: The majority of the subjects wanted to change to the new Harmony processor because of a better understanding in everyday life, handling, and improved battery-life time.

Current steering and results from novel speech coding strategies.

OBJECTIVE: Advanced Bionics' cochlear implants have independent current sources that can share stimulation current between 2 contacts (Current Steering). By stimulating 2 adjacent electrodes with different weights, different pitches can be evoked, allowing to increase the number of processing channels. STUDY DESIGN: A counterbalanced crossover design was used to compare 3 different current steering implementations to the clinical HiRes strategy. SETTING: The study was a prospective, within-subject, repeated-measure experiment. PATIENTS: The study group consisted of 8 postlingually deaf subjects with a minimum of 12-month experience in HiRes. INTERVENTION: The following programs were evaluated: 1) a Fast Fourier Transformation (FFT)-based current steering implementation with 120 stimulation sites; 2) the same current steering implementation but with 16,000 stimulation sites; and 3) a current steering implementation based on a sinusoidal decomposition of the original signal with 16,000 stimulation sites. MAIN OUTCOME MEASURES: Speech perception tests in quiet and in Comité Consultatif International Télégraphique et Téléphonique (CCITT) noise, as well as with competing talker; an adaptive test of the frequency difference limen; a Quality Assessment Questionnaire. RESULTS: Current results do not show any improvement in speech perception for a certain current steering strategy compared with HiRes. However, when selecting the optimal current steering strategy, subjects could achieve a significant benefit compared with the clinical HiRes. In addition, the frequency difference limen could be reduced significantly at 1,280 Hz. CONCLUSION: Current steering seems to have the potential to improve both understanding in adverse listening situations and frequency resolution. However, the optimal implementation needs further investigation.

High power fundamental mode Nd:YAG laser with efficient birefringence compensation.

Experiments on a high-power end-pumped Nd:YAG rod laser with an efficient birefringence compensation will be presented. A linearly polarized output power of 114 W with an M2-value of 1.05 was realized. Furthermore, the from our best knowledge highest injection-locked singlefrequency output power of 87 W in a nearly diffraction-limited beam was demonstrated.